Holding device for wafers

ABSTRACT

The invention relates to a holding device for wafers in an arrangement for wafer inspection, comprising two grippers ( 11, 12 ), each of which, in the closed state of the holding device ( 8 ), encloses a subsection of the wafer circumference and which are connected to a drive device ( 27 ) and, when the latter is driven, the grippers ( 11, 12 ) move away from each other for the purpose of opening the holding device ( 9 ) and move toward each other for the purpose of closing the holding device ( 8 ), and a holding arm ( 13 ), on which the two grippers ( 11, 12 ) are pivotably mounted. 
     In this case the holding arm ( 13 ) is mounted such that it can rotate about an axis (A) which lies substantially in the plane covered by the wafer (W), so that after a rotation through 180° about the axis (A), a wafer (W) held between the grippers ( 11, 12 ) has been turned.

The invention relates to a holding device for wafers in an arrangementfor wafer inspection, comprising two grippers, each of which, in theclosed state of the holding device, encloses a subsection of the wafercircumference and which are connected to a drive device and, when thelatter is driven, the grippers move away from each other for the purposeof opening the holding device and move toward each other for the purposeof closing the holding device, and comprising a holding arm on which thetwo grippers are pivotably mounted.

A holding device of this type is disclosed by U.S. Pat. No. 5,700,046 A.The holding device described there is mounted such that it can move andis used for the purpose of holding wafers as they are transferred, forexample, from a pick-up station to an inspection station. For thispurpose, the holding device can move along a horizontal axis, can bemoved up and down and pivoted about an axis at right angles to thetransport direction. The transport direction and the direction of themain extent of the wafer always lie in one plane in this case, that isto say the alignment of the two opposite surfaces of the wafer withrespect to the transport direction is maintained during the transfer.

During the transfer, the wafer is enclosed in the manner of an arc bythe grippers. In the process, the wafer bears only against theintermediate pieces provided on the grippers. In the holding devicedescribed in U.S. Pat. No. 5,700,046 A, these are constructed in such away that the wafer is held flatly only on its unstructured underside orrear side and at points on its circumferential side edge. Theintermediate pieces are L-shaped for this purpose. In this case, thewafer rests with its underside or rear side on horizontal legs of theintermediate pieces and is kept centered by means of the vertical legs,which bear against the side edge of the wafer.

U.S. Pat. No. 5,807,062 A discloses an inspection arrangement in which awafer passes through various inspection stations. Here, in addition to amicroinspection station, in which a microscopic examination of the waferis carried out, a macroinspection station is also provided, in which thewafer is assessed directly visually by an inspector. In this case, it isprimarily large-area faults which may be detected, such as scratches orcolor deviations. Moreover, contaminants, for example dust particles,adhering to the wafer can be detected.

However, since in the inspection arrangement described in U.S. Pat. No.5,807,062 A the transport direction and the direction for the mainextent of the wafer always likewise lie in one plane, that is to say thealignment of the structured upper side and the nonstructured undersideof the wafer with respect to the transport direction is maintainedduring the transfer, and turning of the wafer is not possible with thisholding device, it is, however, possible to inspect only that surface ofthe wafer which faces the inspector or the microscope objective. This isgenerally the structured upper side of the wafer. From time to time,however, there is an interest in assessing the underside or rear side ofthe wafer as well.

On this basis, the invention is based on the object of providing adevice which permits viewing both of the structured and of thenonstructured surface of a wafer.

To this end, a holding device of the type mentioned at the beginning isproposed in which the holding arm is mounted such that it can rotateabout an axis A, which lies substantially in the plane covered by thewafer, so that after a rotation through 180° about the axis, a waferheld between the grippers has been turned.

The axis A should advantageously run approximately centrally between twopivoting bearings for the grippers.

With the aid of the holding device according to the invention, a wafercan be held securely and turned in any desired transport position of theholding device, that is to say in an inspection station or even halfwaybetween two stations, so that it is possible to inspect both the frontside and the rear side from a defined viewing station. Since the waferis held by the grippers only at a side edge, the view of both itssurfaces is not restricted or only insignificantly restricted.

The holding device is preferably used in an arrangement for the visualinspection of wafers. This arrangement comprises a transfer station, amacroinspection station and a microinspection station and also atransfer device for transporting a wafer between the individualstations. In this case, the holding device is arranged in themacroinspection station.

Therefore, during a passage of a wafer through the inspectionarrangement, both its structured front side and its rear side can beassessed macroscopically.

In this case, it is also necessary to take account of the fact that thewafer must not be put down on its structured front side, since thiscould lead to damage which would make the wafer unusable. With theholding device, such impairment of the front side during the inspectionof the wafer is avoided.

In an advantageous refinement of the invention, the holding arm ismounted such that it can pivot about a further axis B, which runssubstantially tangentially with respect to the wafer circumference andintersects the axis A at least approximately at right angles. This makesit possible to pivot the wafer out of its position before turning it.This is advantageous in particular when components of the waferinspection device could collide with the wafer or the grippers duringturning.

The axis A should advantageously run approximately centrally between twopivoting bearings for the grippers.

Such a collision may also be avoided by the holding arm being mountedsuch that it can be displaced in a rectilinear guide, the displacementdirection C intercepting the axes A and B substantially at right angles.It is also possible in this way to lift the wafer out of its originaltransport plane to such an extent that a collision during turning isavoided.

By means of a combination of the aforementioned possible movements, themovement travel and the pivoting angle may be reduced, as a result ofwhich the time for turning the wafer can be reduced. The movements, thatis to say the translation movement and the pivoting movements of theholding arm, are preferably carried out at the same time.

The possibility of a well coordinated movement sequence results if ineach case separately driveable drive devices are provided for pivotingthe grippers, for turning the wafer by means of rotation about the axisA, for pivoting the holding arm about the axis B and for displacing theholding arm in the displacement direction C.

In a particularly advantageous refinement of the invention, the gripperseach have, on their portions facing the wafer circumference,intermediate pieces, of which at least one is shaped geometrically suchthat the wafer is held only by contact at its circumferential edges. Inthis way, firstly secure holding of the wafer is ensured, secondly anycontact with the front side is avoided. Furthermore, the impairment ofthe visible surface in particular on the rear side of the wafer as well,remains very low. As a result of the very small contact areas, the riskof transferring particles is also reduced.

In principle, it is possible to construct individual intermediate piecesin such a way that these come into engagement with one circumferentialedge and other intermediate pieces come into engagement only with theother circumferential edge of the wafer. However, at least oneintermediate piece is preferably provided, which, during gripping, bearsagainst both circumferential edges of the wafer. Such an intermediatepiece can, for example, be open in a V shape toward the wafer, thecircumferential edges of a wafer that is held resting in the V profile.

Furthermore, it is possible to construct such an intermediate piece as aroller, which is mounted eccentrically on a gripper and can be fixed ina selected angular position. This makes it possible, in a particularlysimple manner, to perform an adjustment of the position between thewafers and the grippers.

As a result of the resilient support of at least one intermediate pieceon a gripper, firstly secure gripping is ensured, secondly thecontraction forces at the points of contact can be managed well, so thatdamage can be avoided with great certainty.

The resilient support can be provided, for example, via a leaf spring,the intermediate piece being attached to the associated gripper by aleaf spring. This has the advantage that the holding force of the springis not impaired during turning. Instead, the position of the waferrelative to the grippers is maintained during turning.

Furthermore, it is also possible to prestress the gripper movementsthemselves resiliently, in order in this way to keep the risk of damageto the circumferential edges of the wafer low, in particular whenclosing the grippers.

In a further advantageous refinement of the invention, at least one stopis provided between the grippers and the holding arm, which limits thepivoting angle during the gripper movement. The security of the holdingdevice is in particular improved thereby.

In order to ensure secure holding of a wafer in the holding device, inparticular even in the event of failure of the operating voltage, atension spring is provided between the grippers, by means of which thewafer is held between the grippers under elastic tension, even withoutany drive force.

In a further advantageous refinement of the invention, a sensor formonitoring the presence of a wafer between grippers is provided on atleast one gripper. This is advantageous in particular for an automatedoperating mode of the holding device, in which a wafer is grippedautomatically, subsequently turned, then rotated back into its originalposition and finally released again.

The invention will be explained in more detail below using an exemplaryembodiment illustrated in the drawing, in which:

FIG. 1 shows a schematic representation of an inspection arrangementhaving a holding device for turning a wafer,

FIG. 2 shows a three-dimensional view of the holding device,

FIG. 3 shows a side view of the holding device in a first positionbefore gripping a wafer,

FIG. 4 shows a side view of the holding device in a second position whengripping a wafer,

FIG. 5 shows a side view of the holding device in a third positionimmediately before turning the wafer, in which position the wafer hasalready been lifted upward and pivoted,

FIG. 6 shows a detailed view of the gripper in the region of the wafer,

FIG. 7 shows a detailed view of an intermediate piece,

FIG. 8 shows a detailed view of a resilient intermediate piece,

FIG. 9 shows a detailed view of a sensor, and

FIG. 10 shows a detailed view of a stop for the grippers.

The first exemplary embodiment shows, in FIG. 1, an inspectionarrangement 1 with which two-dimensional substrates such as wafers W canbe examined both directly visually and also microscopically. Inparticular, by using the inspection arrangement 1, wafers W assessed asfaulty during fabrication and separated out may be examined moreclosely, in order as a result to draw conclusions about the cause of thefault. However, the inspection arrangement can also be used for otherexaminations.

In the exemplary embodiment illustrated, the inspection arrangement 1comprises three stations, at which different tasks or preparatoryactivities are carried out. These three stations, namely a transferstation 2, a macroinspection station 3 and a microinspection station 4are arranged in a common housing 5, which is closed off to the outside.The individual wafers W are transported between the individual stations2, 3 and 4 by means of a transfer device 6. Here, the transfer device 6comprises a star-shaped holder, which rotates about a central axis Z andis stopped at the individual stations.

In the transfer station 2, a wafer W is loaded into the inspectionarrangement 1 by means of a transfer device 7, indicated, and is putdown on the transfer device 6. From there, with a rotation of thetransfer device 6 through 120°, the wafer W passes into themacroinspection station 3. In the latter, an assessment is carried outby means of an inspector P standing or sitting beside the inspectionarrangement 1.

In the transfer state, the structure front side of the wafer W pointsupward, while the unstructured rear side of the wafer W rests on thetransfer device 6. After the front side has been viewed, the wafer W isturned, so that the inspector P can also inspect its rear side. For thispurpose, a holding device 8 is provided in the macroinspection station 3and firstly grips the wafer W, lifts it upward off the transfer device 6and then turns it. Following inspection of the rear side of the wafer,the wafer W is firstly turned back and then put down with the rear sideon the transfer device 6 again.

By indexing the transfer device 6 by 120° again, the wafer W passes intothe microinspection station 4. Here, the wafer W can be examined indetail, section by section, with a microscope 9. The microscope 9comprises a moveable table 10, on which the wafer W to be inspected isput down temporarily for the purpose of inspection. After theinspection, the wafer W is transported onward to the transfer station 2,in which the wafer W is removed by means of the transfer device 7.Suitable transfer devices are known to those skilled in the art andtherefore do not require any specific explanation. For example, use canbe made here of a device as described in U.S. Pat. No. 5,700,046 A.

In the following text, the holding device 8 according to the inventionfor turning a wafer W, arranged in the macroinspection station 3, is tobe explained in more detail.

The holding device 8, which is illustrated in detail in FIG. 2,comprises two arc-shaped grippers 11 and 12 which, in terms of theirshape, are matched to the diameter of the wafers W to be gripped andenclose about three quarters of the wafer at its side edge. The twogrippers 11 and 12 are mounted on a holding arm 13 and can be moved withrespect to each other. In order to open them, the grippers 11 and 12 arepivoted away from each other, so that the inner sides of the gripperscan be guided to the level of the wafer edge. In order to grip a waferW, the holding device is closed, that is to say the grippers 11 and 12are moved toward each other until the latter come into contact with thewafer edge by means of the intermediate pieces 14 and 15.

The intermediate pieces 14 and 15 are in this case constructed in such away that, when they grip a wafer W, they bear only against thecircumferential edges at the wafer circumference, as shown in FIG. 7. Bythis means, firstly secure gripping is ensured, secondly any contactwith the structured front side and also the rear side of the wafer W isavoided. Moreover, the area of contact between the contraction elements14 and 15 and the wafer W remains small, so that as few particles aspossible are loosened or transferred when gripping and releasing thewafer W.

In the selected exemplary embodiment, a total of four uniformlydistributed intermediate pieces 14 are permanently arranged on thegrippers 11 and 12, each being designed in the manner of a roller. Whenviewed in a plane at right angles to the gripping plane, this rollerpossesses a wedge-shaped profile which tapers toward the roller center.The two mutually opposite wedge surfaces 16 and 17 in each case bearagainst a circumferential edge of the wafer W when gripping, and in thisway also effect centering of the wafer W in the gripping plane.

The permanently arranged intermediate pieces 10 are in each case mountedeccentrically on the associated gripper 11 or 12. As a result of arotation, in this way the position of a gripped wafer W relative to thegrippers 11 and 12 can be set. After an adjustment has been carried out,the intermediate pieces 14 are fixed in the selected angular position.

Apart from the stationary intermediate pieces 14, a resilientintermediate piece 15 is also provided, which is shown in detail in FIG.8. In terms of its shape, this intermediate piece 15 correspondssubstantially to half an intermediate piece 14, so that the resilientlymounted intermediate piece 15 can also bear with two wedge surfaces 16and 17 against the circumferential edges of a wafer W. The intermediatepiece 15 is fixed to a leaf spring 18 which, for its part, is in turnfixed to the inner flank of the gripper 11 which points toward the sideedge of the wafer W. The leaf spring 18 can be deflected elastically inthe gripping plane but, on the other hand, is stiff in a direction atright angles to this. This radial springing permits particularly gentlegripping of a wafer W.

Furthermore, in each case a sensor 19 is fitted to the grippers 11 and12, with which the presence of a wafer W between the grippers 11 and 12can be determined. The signal generated by the sensors 19 is evaluatedin a control device, not specifically illustrated, in order to permitautomated operation of the holding device 8. For example, before a waferis turned, it is possible to determine whether said wafer has beengripped properly. Moreover, when the wafer W is put down on the transferdevice 6 again, it is possible to determine whether, before the grippers11 and 12 are removed from the wafer W, the latter has also actuallybeen released. The sensors 19 are constructed and arranged accordingly.In the exemplary embodiment illustrated, they are located on the innerflanks of the grippers 11 and 12.

In order to open and close the grippers 11 and 12, they are pivotablymounted on the holding arm 13. The pivoting movement of the grippers 11and 12 is limited by a stop 20 fitted to the gripper 11. Said stop isillustrated in detail in FIG. 10, which shows a closed position of thegrippers 11 and 12. In this closed position, the stop 20 strikes a stopsurface 21 on the holding arm 13.

Arranged beside the stop 20 is a tension spring, which is connected toboth grippers 11 and 12 in order to pull the latter into the closedposition. This ensures that a wafer W always remains held securelybetween the wafers 11 and 12. The opening and closing are carried out bymeans of a drive device, which is coupled to the grippers 11 and 12.

In order to turn the wafer W, a further drive device is provided, whichpermits rotation of the wafer through 180° about an axis A. Following arotation about this turning axis A, the wafer W is substantially in theinitial position, but the front side and the rear side have beeninterchanged. As FIG. 2 shows, the turning axis W runs through theholding arm 13, parallel to or through the gripping plane, andpreferably also through the mid-axis M of the wafer W.

The holding arm 13 is in turn pivotably mounted on a bracket 23. Thepivot axis B in this case runs transversely with respect to the turningaxis A. In the exemplary embodiment illustrated, the pivot axis B runshorizontally and outside a wafer W gripped between the grippers 11 and12.

The bracket 23 is for its part supported on a base part 24 and guidedlinearly with respect to the latter in the displacement direction C. Thelinear guide 25 here permits an upward and downward movement of thebrackets 23 and therefore, at the same time, of the holding arm 13 andof the grippers 11 and 12.

Each of the individual movements, that is to say the opening and closingof the grippers 11 and 12, the turning of the holding arm 13 with thegrippers 11 and 12 about the turning axis A, the pivoting of the holdingarm 13 about the pivot axis B and also the upward and downward movementof the bracket 23 along the displacement direction C, are carried outvia a separately controllable drive device. In this case, actuating orstepper motors can be provided, so that the individual movements can becarried out completely independently of one another. The individualdrive devices are designated by the designations 26 to 29 in FIGS. 2 to5.

In the following text, the operating mode of the holding device 8 is nowto be explained in more detail using FIG. 3 to FIG. 5. In this case,FIG. 3 shows an initial position, in which a wafer W is conveyed intothe macroinspection station 3 in a transfer plane T by means of thetransfer device 6. In this case, the grippers 11 and 12 are located in aposition underneath the transfer plane T. The gripping plane of thegrippers 11 and 12 is aligned approximately parallel to the transferplane T. In order to grip the wafer W, first of all the drive device 26is actuated in order to move the bracket 23 along the displacementdirection C. Said drive device 26 is constructed as a linear motor 26here. At the same time, the grippers 11 and 12 are opened as a result ofactuation of the associated drive device 27, so that the intermediatepieces 14 and 15 do not collide with the wafer W as they move upward.

The upward movement along the displacement direction C is stopped whenthe gripping plane coincides with the transfer plane T. By means ofrenewed actuation of the drive device 27, an electric motor here, thegrippers 11 and 12 are moved into the closed position, whereupon theintermediate pieces 14 and 15 are brought into contact with the wafer Wand in the process engage around its side edge. This state isillustrated in FIG. 4. When proper gripping of the wafer W is signalledby means of the sensors 19, the drive device 26 is actuated again inorder to lift the wafer W off the transfer device 6 and to move itfurther upward. At the same time, or else with a small time delay, theholding arm 13 is pivoted about the axis B with respect to the bracket23, as indicated in FIG. 5. For this purpose, the associated drivedevice 28, which is again constructed as an electric motor, is actuated.The wafer W is moved upward and pivoted about the axis B until thegrippers 11 and 12 with the wafer W can be rotated without hindranceabout the turning axis A, without colliding with the transfer device 6in the process.

As a result of the possibility of pivoting about the pivot axis B, themovement travel along the displacement direction C can be keptrelatively small. The simultaneity of the two movements makes itpossible to quickly reach the position illustrated in FIG. 5 in whichthe actual turning can then be performed.

The assessment of the rear side of the wafer W can be performed by meansof an appropriate alignment of the holding device 8 in this pivotedposition, from a viewing space beside the inspection arrangement. Forthis purpose, the drive device 29 is actuated in order to rotate aboutthe axis A.

By means of a combined pivoting movement about the axes A and B by smallangles, a tumbling movement with the wafer W can be carried out in theposition illustrated in FIG. 5 and, given appropriate illumination ofthe wafer W, improves the visual detectability of faults on the wafer Wand also dust particles adhering thereto. This tumbling movement can becarried out both for viewing the structured front side and for viewingthe rear side.

However, it is also conceivable to move the wafer W back into a positioncorresponding to FIG. 4, but said wafer is stopped shortly above thetransfer device 6, in order not to damage the structured front side ofthe wafer W. In this way, virtually identical observation conditions canbe implemented for the inspection of the front and rear sides. However,this is somewhat more time-consuming than the inspection in the positionillustrated in FIG. 5, since the pivoting and lifting movements withrespect to the axis B and the displacement direction C then have to becarried out twice.

After the wafer W has been turned back into the position illustrated inFIG. 5, it is then put down with its rear side on the transfer device 6,for which purpose the holding device 8 is moved into the positionillustrated in FIG. 4. The wafer is released by opening the grippers 11and 12. This is also detected by means of the sensors 19. By means oflowering the bracket 23 further, the initial position illustrated inFIG. 3 is then reached, in which the grippers 11 and 12 are pulled backfrom the transfer plane T and are closed in order to relieve the load onthe associated drive device 27.

The holding device explained permits rapid and efficient microscopicinspection of the front and rear sides of a wafer in one operation. As aresult of the arrangement in the macroinspection station, the scope ofthe inspection of an inspection arrangement is increased.

LIST OF DESIGNATIONS

-   1 Inspection arrangement-   2 Transfer station-   3 Macroinspection station-   4 Microinspection station-   5 Housing-   6 Transfer device-   7 Transfer device-   8 Holding device-   9 Microscope-   10 Table-   11 Gripper-   12 Gripper-   13 Holding arm-   14 Intermediate piece-   15 Resilient intermediate piece-   16 Wedge surface-   17 Wedge surface-   18 Leaf spring-   19 Sensor-   20 Stop-   21 Stop surface-   22 Tension spring-   23 Bracket-   24 Base part-   25 Linear guide-   26, 27, 28, 29 Drive devices-   W Wafer-   R Axis of rotation-   A, B Axes-   C Displacement direction-   M Mid-axis

1. A holding device for wafers in an arrangement for wafer inspection,comprising: two grippers (11, 12), each of which, in the closed state ofthe holding device (8), encloses a subsection of the wafer circumferenceand which are connected to a drive device (27) and, when the latter isdriven, the grippers (11, 12) move away from each other for the purposeof opening the holding device (9) and move toward each other for thepurpose of closing the holding device (8), and a holding arm (13), onwhich the two grippers (11, 12) are pivotably mounted, wherein theholding arm (13) is mounted such that it can rotate about an axis (A)which lies substantially in the plane covered by the wafer (W), so thatafter a rotation through 180° about the axis (A), a wafer (W) heldbetween the grippers (11, 12) has been turned; and, wherein said holdingarm (13) is mounted such that it pivots about an axis B, which runssubstantially tangentially with respect to the wafer (W) circumferenceand intersects the axis A at least approximately at right angles andwherein said holding arm (13) is mounted such that it is displaced in arectilinear guide, the displacement direction C intercepting the axes Aand B substantially at right angles.
 2. The holding device as claimed inclaim 1, further comprising two pivot bearings attached to said grippers(11, 12) wherein said axis (A) runs approximately centrally between saidtwo pivoting bearings.
 3. The holding device as recited in claim 1,wherein a separate drive device (26, 27, 28, 29) is provided for eachof: pivoting the grippers (11, 12); turning the wafer (W) by means ofrotation about the axis (A); pivoting the holding arm (13) about theaxis (B,); and, displacing the holding arm (13) in the displacementdirection (C).
 4. The holding device as recited in claim 1, furthercomprising intermediate pieces (14, 15), said intermediate pieces (14,15) located on the portions of said grippers (11, 12) facing at leastone wafer circumferential edge, at least one of said intermediate pieces(14, 15) shaped geometrically to hold said at least one circumferentialedge of said wafer (W).
 5. The holding device as recited in claim 4,wherein at least one of said intermediate pieces (14, 15), bears againstboth circumferential edges of the wafer (W) during gripping.
 6. Theholding device as recited in claim 5, wherein the at least oneintermediate piece (14, 15) is configured in a V shape toward the wafer(W), wherein said both circumferential edges of a wafer (W) are heldwithin the acute angle of the at least one V shaped intermediate piece(14, 15).
 7. The holding device as recited in claim 5, wherein at leastone intermediate piece (14, 15) is constructed as a roller, said rollerbeing mounted eccentrically on at least one gripper (11, 12) and fixedin a selected angular position.
 8. The holding device as recited inclaim 5, wherein the at least one of said intermediate pieces (14, 15)is resiliently attached to said gripper (11, 12).
 9. The holding deviceas claimed in claim 8, wherein the at least one resiliently attachedintermediate piece (14, 15) is attached to said gripper (11, 12) by aleaf spring (18).
 10. The holding device as recited in claim 1, whereinsaid grippers (11, 12) are resiliently prestressed in their pivotingbearings.
 11. The holding device as recited in claim 1, furthercomprising stops (20), said stops (20) positioned between said grippers(11, 12) and said holding arm (13), wherein said stops (20) limit thepivoting angle during the gripper movement.
 12. The holding device asrecited in claim 1, further comprising a tension spring (22), saidtension spring (22) connecting said grippers (11, 12), wherein saidwafer (W) is held between said grippers (11, 12) under elastic tension.13. The holding device as recited in claim 1, further comprising asensor (19) on at least one of said grippers (11, 12), wherein saidsensor (19) detects the presence of a wafer (W) between the grippers(11, 12).
 14. A holding device for wafers in an arrangement for waferinspection, comprising: two grippers (11, 12), each of which, in theclosed state of the holding device (8), encloses a subsection of thewafer circumference and which are connected to a drive device (27) and,when the latter is driven, the grippers (11, 12) move away from eachother for the purpose of opening the holding device (9) and move towardeach other for the purpose of closing the holding device (8) a holdingarm (13), on which the two grippers (11, 15 12) are pivotably mounted,and, at least two intermediate pieces (14, 15) located on the portionsof said grippers (11, 12) facing at least one wafer circumferentialedge, at least one of said intermediate pieces (14, 15) shapedgeometrically to hold said at least one circumferential edge of saidwafer (W) characterized in that the at least two intermediate pieces(14, 15) are resiliently supported on said gripper (11, 12) by a leafspring (18); wherein the holding arm (13) is mounted such that it canrotate about an axis (A) which lies substantially in the plane coveredby the wafer (W), so that after a rotation through 180° about the axis(A), a wafer (W) held between the grippers (11, 12) has been turned. 15.The holding device as recited in claim 14, wherein the at least one ofsaid intermediate pieces (14, 15) bears against both circumferentialedges of the wafer (W).
 16. The holding device as recited in claim 15wherein the at least one intermediate piece (14, 15) bearing againstboth circumferential edges of the wafer (W) is configured in a V shapetoward the wafer, wherein said both circumferential edges of the wafer(W) are held within the acute angle of said at least one V shapedintermediate piece (14, 15).
 17. The holding device as recited in claim14 wherein at least one intermediate piece (14, 15) is constructed as aroller, said roller being mounted eccentrically on at least one gripper(11, 12) and fixed in a selected angular position.
 18. The holdingdevice as recited in claim 14, wherein said holding arm (13) is mountedsuch that it can pivot about a further axis (B), said further axis (B)extending substantially tangentially with respect to a wafer (W)circumference and intersecting the axis (A) at least approximately atright angles.
 19. The holding device as recited in claim 18, wherein theat least one of said intermediate pieces (14, 15) bears against bothcircumferential edges of the wafer (W).
 20. The holding device asrecited in claim 19 wherein the at least one intermediate piece (14, 15)bearing against both circumferential edges of the wafer (W) isconfigured in a V shape toward the wafer, wherein said bothcircumferential edges of the wafer (W) are held within the acute angleof said at least one V shaped intermediate piece (14, 15).
 21. Theholding device as recited in claim 18 wherein at least one intermediatepiece (14, 15) is constructed as a roller, said roller being mountedeccentrically on at least one gripper (11, 12) and fixed in a selectedangular position.